1. Field of the Invention
The present invention relates to a thin-film magnetic head for recording that is used with, for example, a flying magnetic head or a contact magnetic head and, more particularly, to a thin-film magnetic head capable of properly supporting narrower tracks to successfully cope with the trend toward a higher recording density, and a manufacturing method for the same.
2. Description of the Related Art
With the recent trend toward higher recording densities, there has been a demand for a structure of a thin-film magnetic head for recording known as “an inductive head” that is capable of restraining the occurrence of side fringing, in particular, in achieving narrower tracks. The side fringing refers to the magnetic field leakage in the direction of a track width.
Conventionally, there have been, for example, the following two feasible structures for the inductive head capable of properly restraining the occurrence of the side fringing.
FIG. 16 is a partial longitudinal sectional view showing the structure of a conventional inductive head. The term “longitudinal section” means a section taken in a direction parallel to the plane formed along axis Y and axis Z shown in the drawing. The same applies hereinafter.
A lower core layer 1 is formed of a NiFe-based alloy or the like. A gap depth (Gd) defining layer 2 formed of a resist or the like is deposited on the lower core layer 1. The Gd defining layer 2 has, for example, a semi-elliptical longitudinal section, as shown in FIG. 16. The gap depth (Gd) is determined by the distance from a front edge surface 2a of the Gd defining layer 2 to the front edge surface of the thin-film magnetic head. It has been considered that recording characteristics typically represented by overwrite characteristics can be improved by forming the Gd defining layer 2 so as to narrow a recording magnetic field at the neighborhood of the gap.
In the structure shown in FIG. 16, a magnetic pole laminate 6, which is constituted by a lower magnetic layer 3, a gap layer 4, and an upper magnetic pole layer 5 that are deposited in this order from bottom to top, is formed on the lower core layer 1, extending from the front edge surface of the thin-film magnetic head onto the Gd defining layer 2 in the height direction (direction Y shown in the drawing). At the rear end side of the magnetic pole laminate 6, an insulating layer 7 formed of Al2O3 or the like is deposited in the height direction.
A coil layer 8 is formed such that it wraps the insulating layer 7, the coil layer 8 being covered by an organic insulating material layer 9.
A upper core layer 10 made of a magnetic material is deposited such that it extends from the top of the upper magnetic pole layer 5 constituting the magnetic pole laminate 6 to the top of the organic insulating material layer 9. A proximal end portion 10b of the upper core layer 10 is magnetically connected onto the lower core layer 1.
In the inductive head having the construction shown in FIG. 16, a track width Tw is restricted by the width of the upper magnetic pole layer 5 in a track width direction (direction X in the drawing). This width is smaller than the width in the track width direction of a distal end portion 10a of the upper core layer 10. It has been considered that forming the magnetic pole laminate 6 restricting the track width Tw between the upper core layer 10 and the lower core layer 1 makes it possible to properly restrain the occurrence of side fringing and to permit support of narrower tracks.
FIG. 18 is a partial longitudinal sectional view showing the structure of another conventional inductive head. The layers denoted by like reference numerals shown in FIG. 16 indicate the like layers as those shown in FIG. 16.
In the structure illustrated in FIG. 18, a second lower core layer 11 is deposited on the lower core layer 1 such that it extends in the height direction or direction Y in the drawing from the front edge surface of the thin-film magnetic head. An insulating layer 7 is formed at the rear of the second lower core layer 11 in the height direction, and a gap layer 12 formed of an insulating material, such as Al2O3, is deposited such that it extends from the top of the second lower core layer 11 to the top of the insulating layer 7.
A second upper core layer 13 that extends in the height direction (direction Y in the drawing) for a predetermined length from the front edge surface of the thin-film magnetic head is deposited on the gap layer 12. At the rear of the second upper core layer 13 in the height direction, an insulating layer 14 made of Al2O3 or the like is formed. Referring to FIG. 18, a rear edge surface 13a of the second upper core layer 13 is positioned farther in the height direction (direction Y in the drawing) than a rear edge surface 11a of the second lower core layer 11. The distance from the front edge surface of the thin-film magnetic head of the second lower core layer 11 to the rear edge surface 11a determines the Gd. The rear edge surface 13a of the second upper core layer 13 has been positioned farther toward the rear in the height direction than the rear edge surface 11a of the second lower core layer 11, as mentioned above, primarily in order to maximize the area of contact between the second upper core layer 13 and the upper core layer 10. This arrangement permits higher magnetic flux efficiency.
A coil layer 8 is formed such that it wraps the insulating layer 14, and the coil layer 8 is covered by an organic insulating material layer 9.
An upper core layer 10 is deposited such that it extends from the top of the second upper core layer 13 to the top of the organic insulating material layer 9. A proximal end portion 10b of the upper core layer 10 is magnetically connected onto the lower core layer 1.
The inductive head having the construction shown in FIG. 18 has been subjected to the processing described below so as to properly restrain side fringing.
Referring to FIG. 19, which is a partial front view of the inductive head of FIG. 18 that is observed from the front edge surface of the thin-film magnetic head or as indicated by the chain line shown in FIG. 18, both symmetrical surfaces 11c in the track width direction (direction X in the drawing) of the second lower core layer 11 are first trimmed by ion milling from substantially vertical direction A with respect to the surface of the lower core layer 1 (hereinafter referred to as “depth trimming”) so as to form a projection 11b, which projects toward the second upper core layer 13, on the second lower core layer 11. Thereafter, the materials adhered again to both side edge surfaces 13b in the track width direction (direction X in the drawing) of the second upper core layer 13 are removed. Then, ion milling is carried out from a direction B aslant with respect to the direction perpendicular to the surface of the lower core layer 1 in order to form further narrower tracks. This ion milling will be hereinafter referred to as “side trimming.” Thus, both symmetrical surfaces 11c of the second lower core layer 11 are provided with slant surfaces in which the thickness of the second lower core layer 11 gradually decreases as the distance from the proximal end of the projection 11b increases in the track width direction (direction X in the drawing).
In the inductive heads of the types shown in FIG. 18 and FIG. 19, respectively, the track width Tw is restricted by the width in the track width direction (direction X in the drawing) of the second upper core layer 13. The second lower core layer 11 has the projection 11b located at the position opposing the second upper core layer 13. The constructions of the inductive heads shown in FIGS. 18 and 19 have been therefore considered to permit proper support of narrower tracks to properly restrain the occurrence of side fringing.
Successfully achieving narrower tracks requires restraint of the occurrence of side fringing mentioned above and a recording magnetic field that has higher intensity in the vicinity of a gap and has stable intensity. Unless these conditions are satisfied, recording characteristics, including an overwrite characteristic, deteriorate, making it impossible to fabricate a thin-film magnetic head for higher recording densities that exhibit effective compatibility with narrower tracks.
It has been found, however, that the inductive heads having the two structures described above both pose problems with the intensity of a recording magnetic field in the vicinity of a gap or with the stability of the recording magnetic field.
FIG. 17 is a partial enlarged longitudinal sectional view showing the structure of the neighborhood of the magnetic pole laminate 6 of the inductive head shown in FIG. 16. FIG. 17 illustrates a step of the process for forming the magnetic pole laminate 6.
Referring to FIG. 17, a Gd defining layer 2 made of a resist or the like is deposited on the lower core layer 1, then a resist layer 15 pattern-formed by exposure and development is deposited from the middle of the top of the Gd defining layer 2 to the top of the lower core layer 1.
Within the pattern formed on the resist layer 15, a lower magnetic pole layer 3, a gap layer 4, and an upper magnetic pole layer 5 are successively formed by plating in this order from bottom to top. In this case, the Gd defining layer 2 is made of an insulating material, such as a resist, so that plating growth is not very successful in the vicinity of a rear end 3a on the Gd defining layer 2 of the lower magnetic pole layer 3. As a result, the area in the vicinity of the rear end 3a of the lower magnetic pole layer 3 becomes extremely thin, and hence, the lower magnetic pole layer 3 is undesirably formed to have a curved surface.
Accordingly, a rear end 4a of a gap layer 4 formed by plating on the lower magnetic pole layer 3 is also curvedly formed.
Essentially, the gap layer 4 should be formed to have a flat surface in the direction parallel to the surface of the lower core layer 1. However, the structure having the Gd defining layer 2 shown in FIG. 16 tends to cause the gap layer 4 to be curvedly formed, presenting the problem of unstable recording characteristics.
Furthermore, as shown in FIG. 17, a rear end 5a of the upper magnetic pole layer 5 formed to extend farther in the height direction (direction Y in the drawing) than the gap layer 4 onto the Gd defining layer 2 at the rear is formed on the Gd defining layer 2. Hence, the rear end 5a of the upper magnetic pole layer 5 cannot be grown by plating to a proper thickness. The rear end 5a will be extremely thin.
Furthermore, a gap 5b tends to be formed between the rear end 5a of the upper magnetic pole layer 5 and the resist layer 15, as shown in FIG. 17. The gap 5b leads to a smaller area of an upper surface 5c of the upper magnetic pole layer 5 that is to be in contact with a distal end portion 10a of the upper core layer 10. This frequently causes a drop in the intensity of a recording magnetic field leaking from the vicinity of the gap.
Thus, in the step illustrated in FIG. 17, the Gd defining layer 2 for deciding a gap depth is likely to be responsible for a curved gap layer 4 or for a thin rear end 5a of the upper magnetic pole layer 5. This frequently causes the magnetic pole layer to be magnetically saturated, or leads to a smaller area of contact between the upper magnetic pole layer 5 and the upper core layer 10. These factors have been posing the problems with a drop in the intensity or unstable intensity of a recording magnetic field in the vicinity of the gap, frequently resulting in degradation of characteristics, including an overwrite characteristic.
Furthermore, in order to secure, for example, a predetermined volume of the upper magnetic pole layer 5, a resist layer 15 shown in FIG. 17 is formed to be thick and a deep pattern is formed on the resist layer 15. This allows the upper magnetic pole layer 5 formed in the pattern to be thicker. In this case, however, the patterning accuracy in forming the pattern of the magnetic pole laminate 6 in the resist layer 15 is deteriorated, and the pattern is apt to expand in the track width direction, preventing an inductive head capable of supporting narrower tracks from being achieved.
A problem with the structure of the inductive head shown in FIG. 18 will now be described. Referring to FIG. 19, when depth trimming in direction A or side trimming in direction B is carried out, both side edge surfaces 13b and 13b of the second upper core layer 13 are apt to be formed wavily rather than flatly. In addition, a re-adherent film 7a of an insulating layer 7 formed of Al2O3 or the like tends to remain on the both side edge surfaces 13b. 
The wavy side edge surfaces 13b of the second upper core layer 13 described above have led to an unstable track width Tw, preventing the track width Tw from being always a predetermined value.
The problem of the unstable track width Tw described above is considered due to a rear edge surface 13a of the second upper core layer 13 being formed such that it extends farther toward the rear in the height direction from a rear edge surface 11a of the second lower core layer 11, as illustrated in FIG. 18.
FIG. 20 is a partial perspective view showing a step of depth trimming and side trimming. Referring to FIG. 20, the rear end of the second upper core layer 13 is covered by a resist layer 16, then the exposed gap layers 12 on both sides of the second upper core layer 13, which are not covered by the resist layer 16, and a part of the second lower core layer 11 thereunder are trimmed by depth trimming in directions A in the drawing so as to form the projection 11b of the second lower core layer 11.
However, the rear edge surface 13a of the second upper core layer 13 extends farther toward the rear in the height direction beyond the rear edge surface 11a of the second lower core layer 11, so that a rear end region 7a of the insulating layer 7 that expands to the rear end of the second lower core layer 11 is exposed rather than being covered by the resist layer 16 when the aforesaid depth trimming is carried out. Hence, the rear end region 7a of the insulating layer 7 is also trimmed, and an element of the insulating layer 7 that comes flying adheres, in the form of the film 7a made of the above insulating material, to both side edge surfaces 13b of the second upper core layer 13. The amount of the adhesion varies all over the both side edge surfaces 13b of the second upper core layer 13 rather than being constant, thus leading to unstable configurations of the track width.
In the step for narrowing the track width Tw by side trimming in directions B in the drawing, when removing the adherent film 7a by the side trimming, a thinner portion of the adherent film 7a is removed sooner since the thickness of the adherent film 7a varies from one portion to another. As a result, even both side edge surfaces 13b of the second upper core layer 13 are susceptible to the side trimming. Especially because the adherent film 7a is formed of an insulating material and exhibits a slower milling rate, as compared with a magnetic material, in order to effectively remove the adherent film 7a from the second upper core layer 13, it would be necessary to prolong the milling time or to carry out high-energy ion milling. Thus, the both side edge surfaces 13b of the second upper core layer 13 are partially subjected to intense influences by ion milling during the side trimming operation, and the both side edge surfaces 13b are trimmed to be wavy. Moreover, the rear end region 7a of the exposed insulating layer 7 is also trimmed during the side trimming operation, causing the re-adherent film 7a of the insulating layer 7 to stick to the entire both side edge surfaces 13b of the second upper core layer 13. Thus, there has been a problem in that the track width Tw of a predetermined dimension cannot be achieved.
The failure to obtain the track width Tw of a predetermined dimension causes the intensities of recording magnetic fields in the vicinity of gaps to vary from one product to another, preventing improved quality from being accomplished. This has been making it impossible to fabricate an inductive head capable of successfully supporting narrower tracks.